Blog describing how to convert to live frugally, and eco-friendly.
It also describes on how to do so in a more economical (lower-cost) way than how you've been living before. Also contains a household budget spreadsheet for you to use as a template and assess the economics of the approach.

List of green retrofits

The following is a list of green retrofits that can be done in the house, and on your vehicle. This list allows you to quickly compare what green retrofits you are (still) capable of doing, and where the most financial (and/or ecological) benefit can be attained.

House
1: Install a wood stove with heat exchanger for your central heating system (hot water piping to radiators)
OR install a heat exchanger on your existing stove, fireplace or fireplace insert, and connect it to your central heating system

2: If you use a fuel-oil based burner for your central heating system, swap from using fuel-oil to straight vegetable oil (of which the oil crops are replanted continuously). If you use a a natural gas burner, either change from using natural gas to biogas or to convert your natural gas burner to run on either biobutanol, ethanol or straight vegetable oil.

3: If you're using a non-electric water heater (with or without tank), convert the internal heater from using natural gas to run on either biobutanol, ethanol or straight vegetable oil. If you have an electric water heater, keep it as is. You could also attach a solar thermal collector on your water heater regardless on whether you have an electric or non-electric water heater.

4: Add insulation just below the roof of your house. You can also place climbing plants next to your house's walls (making what's called a "green facade") to decrease temperature fluctuations in your house. Another thing you can do to increase the insulative value of your roof is to add an extensive green roof . Adding an extensive green roof is only possible though if you have a roof that is sloped no more than 5%. It increases the lifespan of the waterproof membrane on your roof as well.

5: Install a rainwater tank to water your plants (using 300 or 500liter rainwater tanks/barrels) and/or add a pipe with a tap to your rainwater piping directing water directly to your garden
OR install a large rainwater tank (3000 to 10000 liter) complete with pump, and pressure vessel, and connecting straight to your flush toilets and/or taps in your house.

6: Make a culinary herb patch, vegetable patch, and/or plant some fruit trees in your garden. Also make a pallet compost bin. You can also buy some chickens and/or a goat and keep it in your garden. Alternatively, you can also keep fish if you have a pond.

7: Start using biobutanol or ethanol in your lawnmower (if you have a non-electric lawnmower)

8: Install a battery energy storage system (nickel iron batteries, industrial deep-cycle batteries, ...) and connect it to all your appliances and have the batteries recharged by the mains electricity grid
OR install a battery storage system (nickel iron batteries, industrial deep-cycle batteries, ...) but just connect it to a section of your appliances (ie lighting, ...), and keep the other section of your appliances simply directly connected to the mains electricity grid

9: Install a renewable energy power plant and connect it to your battery energy system and disconnect entirely from the mains electricity grid
OR install a a renewable energy power plant and connect it to your battery energy
system while keeping a connection to the mains electricity grid (hence forming a grid-tied system with net metering)

10: Install a biogasifier to generate biogas from the biowaste coming from the flush toilets

Car
12: Convert your diesel car to run on straight vegetable oil
OR Convert your diesel car to run on biodiesel

13: Start using biobutanol or ethanol in your gasoline car

Remarks
1: You might not always be able to place the wood stove where you'd like (it will depend on where you can attach to the hot piping system). Stoves need oversight/monitoring, so it's best placed somewhere in the living area. The same problem of not always being able to connect to the hot water piping goes for conversions of fireplaces and fireplace inserts. However, fireplaces and fireplace inserts are generally all ready located in the living area, so the oversight problem won't be had here. Don't use it to help heat any water for showering, ... as it only has benefit for heating the hot water of the radiators (in summer, you won't use your radiators/central heating system, but you would still need hot water for showering, hence the reason why that wouldn't work).

2: By changing to straight vegetable oil (ie rapeseed oil, camelina oil, peanut oil, olive oil, ...) as the fuel for your burner, fuel costs could be much lower in comparison to natural gas or fuel-oil. If you change from natural gas to biogas, costs for the fuel would not be lower. However, in both instances, it will allow you to almost completely eliminate the CO² compensation costs you might otherwise do (only those CO² emissions of electricity and perhaps your car's emissions might still need to be bought, but the amount of these emissions is negligable vs your emissions from heating your house). As such, even in the case of swapping to biogas, total costs too could be much less.
In case there is no supplier of biogas in your region, you might be able to convert your natural gas burner to run on straight vegetable oil instead. If that wouldn't work, you could use biobutanol or ethanol, however the fuel costs would then be substantially higher (you would however have lower CO² emissions you'd need to compensate, so that would reduce those costs a bit at least). An alternative solution might be to use straight vegetable oil yet preheat the oil, at least during start-up, as it's the ignition that might prove a problem. (once its operating, no preheating would be needed anymore). Preheating could be done, for example using an electric heater. Keep in mind however that if you use one of these fuels, you'd also need to place a fuel tank, as neither straight vegetable oil, biobutanol or ethanol is being piped to houses in most areas. With biogas, you might not need to install a tank, however, again, it might not always be available in your area.
If you are unable to change the fuel however, you could just sell the entire burner, and buy and install a tankless electric hot water heater instead (so similar as what you might use to heat the water for your taps, shower, ... The hot water heater could then be placed where the burner used to stand, and connect at the same piping of the central heating system. This solution would be much cheaper than using seperate electrical heaters (electric radiators, convectors, ...), and allows you to keep using your hot water radiators. By using an electric hot water heater (for example from power generated from renewable sources, i.e. using a "green power" subscription from a local power company), you'd also be able to reduce the CO² compensation costs you'd otherwise need to do, by a substantial amount. When counting in these CO² emission reductions you would otherwise buy, it would be cheaper than by remaining to use natural gas or fuel-oil (otherwise, when just comparing the costs of the fuels, it would be more expensive; at least when you don't also integrate solar thermal collectors, use off-peak electricity -i.e. using your battery bank you might own-, use the renewable energy power plant(s) you might own, ...). One additional advantage you'll also have when starting to use an electric hot water heater is that you would no longer be dependant on your fuel supplier for heating your house, meaning gas cutoffs during winter will no longer be possible.

3: Only buy and attach a solar thermal collector if you have a flat roof, or if you have a steep roof, but when your house's roof is optimally oriented (towards the south) and can be optimally tilted using a custom mounting frame.

4: Whereas adding insulation below the roof of your house is a popular solution, and very effective to reduce heating costs, and reduce the CO² compensations you might buy, it is only practical if you haven't all ready added sufficient insulation below your roof (which might or might not be the case). Also, even if you don't yet have sufficient insulation, it might still be difficult to achieve, especially if you have a dropped ceiling. Note that besides insulating the roof, you can't really insulate any other sides of the house (walls, ...), at least not easily, so just focus on the roof or skip it entirely if the roof can't be insulated easily.

5: The first solution is by far the cheapest solution, and also the easiest one to accomplish in practice. You just need to dig in the rainwater barrel or tank into the ground (below frost line) and connect it to the rainwater piping which are hooked up to the gutters. You'll also need to have a pipe sticking out of the ground in which you
can insert your manual pump's inlet pipe. Old manual waterpumps may
still be obtainable in your area, or you can buy the KickStart Hip Pump, or make your own PVC pump.
In countries where it doesn't freeze at all, you won't even need to dig
in the tank completely, and instead, you could just use a bucket to
collect water from it -ie via a built-in tap on the tank at the bottom,
or an open top-. The overflow can connect to the sewerage (in case that was all ready the
case before you converted it) or you can have it run to the garden.
A variant to this is to not use any tank at all, but just connect a pipe with a valve straight on your rainwater pipe, directing water directly to the garden. It isn't even necessary to have the pipe run to near where your plants are; rather, their roots will be able to find the water anyway. A tap is best added so you can easily close off this added pipe and redirect the water again to the initial pipe (which for example connected to the sewerage). This tap is useful if you find that the earth has been saturated enough for the time being. Also, you can also use a combination of both these solutions (directing water straight to the garden from your rainwater pipe, and using a water tank, and overflow to the garden or to the sewerage). Using a combination may be more practical/efficient in instances where you have several roof parts collecting rainwater and thus several rainwater pipes as well.
If you don't know where the rain pipes are in the ground, refer to your building plans (which should have been supplied to you by your architect).
The second solution (installing a large rainwater tank complete with pump,
and pressure vessel, and connecting straight to your flush toilets
and/or taps in your house) will allow you to use your water much more effectively/use more of it. However, it's also much harder to do in practice, and costs a lot more. On the long run however, it may be even much more economical though.

6: Making a culinary herb patch will probably allow you to save most money at least considering the little effort that you need to put in. A vegetable patch too allows you to save quite a bit of money as vegetables too are rather expensive nowadays. Wooden boxes with a glass plate on it ("cold frames") can allow you to extend your growing/harvest season for herbs and cost little. Fruit trees finally also save you money, but as often, more fruit is produced in the harvest season than what you can actually consume in that period, you'd need to also combine it with preservation methods (ie making jam of it, drying -ie using a home made solar dehydrator-, ...)
Chickens are small enough to keep in your garden and also require few maintenance and housing costs. The same goes for a goat, all though you would need a somewhat larger garden for that. You would also need to set up fencing for the chickens (or use a chicken tractor), with a goat you can have it fastened with a long rope to a post. With both, you might feed it (to some degree) with leftover kitchen scraps and/or garden waste (leaves, worms, ...). Any leftover kitchen scraps or garden waste that the animals don't eat can be put on the compost bin (or immediately dug into the soil, which is also called "trench composting"). Don't try to hold anything larger than a goat though (no cows, ...) as these require far too much space for most, are less hygienic to keep, and produce too much dairy for most families anyway. Fish can also be kept, for example if you have a (freshwater) pond. Do make sure however your pond is then balanced out enough (oxygen plants, submerged plants, filtering medium (lava stone, ...), filtering plants rooting in lava stone, pump, ...), that your pond is deep/large enough to cope with temperature changes, and that you're not keeping too much fish neither. Else, you might end up with having algae and dead fish (due to too little oxygen being in it).

7: If you have a non-electric (4-stroke, gasoline) lawnmower, you can only use biobutanol or ethanol. Biobutanol would work immediately, with ethanol, the carburettor's settings may need to be changed, you could ask to have this done in a local garage
if you don't know how to do this.
Regardless of whether you'd
switch to biobutanol or ethanol, you'll be able to reduce the CO² compensations you'd otherwise need to buy considerably.

8: the first solution is obviously the cheapest one, as you don't need as much battery capacity as with the second solution. Depending on what appliances you select it may also allow you to save on parts you might otherwise need. For example, some appliances may be able to run directly on DC power too (i.e. LED lighting, ...), meaning you don't need an inverter to transform the DC power from the battery to AC power for those appliances. Also, you might be able to avoid needing additional transformers, ... As such, it may be useful to examine your current electrical system first, and perhaps do some changes here and there (for example, changing some or all of your incandescent or halogen lamps to LED lightbulbs, LED or LEC strips). This would reduce your energy consumption a bit, and hence also reduce the battery capacity you need.
The second solution is more expensive, but does allow full independence from the grid for a limited duration (ie as in the case of a temporary power outtage); the first solution only allows partial independance (ie during power outtages, your lights, ... can be made to still work, but you'll lose the ability to use other appliances). Both solutions will allow you to save some additional money (10 to 50 euro) as you'll also have the ability to recharge your battery to power some or all of your appliances during off-peak hours (off-peak hours are generally from 22:00hr to 07:00hr). You would be able to set it during that period to recharge by using a time switch.

9: as discussed in the "Household budget spreadsheet" post, what system ends up being the most economical depends on how your energy company charges you for the power you consume. As too mentioned in that post, renewable power plants you could use include:
* PV panels (which you might all ready own)
* small-scale wind turbine
* microhydro power plant
*
biofuel-powered internal combustion engine with attached alternator or
dynamo; note that the internal combustion engine can also be used to heat
your water (ie for showering, ...) as well.
If you were to use a biofuel-powered internal combustion engine, you could optionally also grow some own biofuel crops (i.e. containing straight vegetable oil, ...) yourself. There are also other uses you might have for the oil, such as making soap (and other cleaning agents) with it.
If you all ready have PV panels installed on your roof, you may want to make sure the tilting has been done correctly, and if it isn't, calculate out the the optimal inclination, and adjust the mount frame accordingly, or have this done by a professional. Also, if besides the inclination, the direction -i.e. towards the south in countries in the northern hemisphere- is also incorrect, you may want to see whether there isn't another location where you can place the PV panels instead.
A list of other suitable small-scale power plants can be found here.

10: I mentioned this for reference sake; all though this might seem a good idea at first, the biogas that can be created (even by a family of 4) is nowhere near sufficient to run say your internal combustion engine on it (assuming you have one, ie to recharge your battery energy storage system). It's only useful for say cooking and lighting purposes, by using direct incineration of it (for this reason it's being used a lot in certain developing countries).

11: It may not seem like much, but inserting all the power plugs of your appliances to a socket outlet box with integrated on/off switch allows you to switch off many devices at once, which is still practical to do in real life, and allows you to make sure those appliances no longer draw any "standby" power. Socket outlet boxes don't cost a lot, and will allow you to save quite a bit of money as some appliances (TV's, ...) may still draw say 50% of their power even when not operating.

12: Converting your diesel car to be able to run on straight vegetable oil can be done by bying a conversion kit (which contain electric preheaters for the oil, an oil filter and an extra pump to increase pump pressure). These kits are available by many manufacturers, see here. You can do the conversion yourself, or just have a local garage/mechanic do it.
If you are unable to do it yourself, or find a local garage/mechanic to do it for you, you can also just buy biodiesel, which is straight vegetable oil that is chemically treated so that it will run in any diesel engine. Regardless of what method used, you'll be able to reduce the CO² compensations you'd otherwise need to buy considerably.

13: If you have a gasoline car, you can only use biobutanol or ethanol. Biobutanol would work immediately, with ethanol, it would work only if you have a car with a carburettor (with direct injection, it can work too, but it's much more complicated as you'll need to modify the engine control unit). The carburettor would need to have its settings changed, you could ask to have this done in a local garage if you don't know how to do this.
Regardless of whether you'd switch to biobutanol or ethanol, you'll be able to reduce the CO² compensations you'd otherwise need to buy considerably.
Note that some other options for gasoline cars exist, such as converting to electric (by swapping the engine with an electric engine and adding batteries), or swapping the gasoline engine with a diesel engine (see above). Both these methods however tend to be very expensive options, and technically tricky. Best not to do this as such, unless you have a great amount of technical know-how.